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    SubjectRe: [PATCH v2] [watchdog] combine nmi_watchdog and softlockup
    On Fri, Apr 16, 2010 at 04:46:17PM +0200, Frederic Weisbecker wrote:
    ...
    > > > > + if (hardlockup_panic)
    > > > > + panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
    > > > > + else
    > > > > + WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
    > > > > +
    > > > > + cpumask_set_cpu(this_cpu, to_cpumask(hardlockup_mask));
    > > >
    > > >
    > > >
    > > > May be have an arch spin lock there to update your cpu mask safely.
    > > >
    > >
    > > Hmm, this is NMI handler path so from what we protect this per-cpu data?
    > > Do I miss something? /me confused
    >
    >
    > The cpu mask is not per cpu here, this is a shared bitmap, so you
    > can race against other cpus NMIs.
    >
    > That said, as I suggested, having a per cpu var that we set when we
    > warned would be much better than a spinlock here.
    >

    yeah, saw DECLARE_BITMAP but read it as DEFINE_PER_CPU for some reason.
    having any spinlock in irq handler is really under suspicious.

    -- Cyrill


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